Answer Happy

(a) What are the differences between the features and
arrangements in final circuits for ring circuit
and redial circuit of 13A sockets?
(4 marks)
(b) In a 3-phase-4-wire final circuit of an electrical
installation, the equivalent total loads on the
three phases L1, L2, and L3 are (2+a, j1) R2, (1+b, j3) 2 and (3+c,
j4) 92, respectively. The
supply is a slightly unbalanced three-phase source with its neutral
point earthed, and the voltages
of the three phases L1, L2, and L3 at the source are 21020° V,
220<-120° V and 220<120° V,
respectively. If now the connection between the star point of the
supply and the star point of the
load is broken, determine:
(i)
the voltage of the star-point of the load, with respect to
earth;
(8 marks)
(ii)
the load currents in the three phasys lines and the neutral wire,
before and after the broken
neutral; and
(4 marks)
(iii)
the phase voltages across each of the three phases of the loads
after the broken neutral, and
comment on their values. Hence, discuss the need of installing a
fuse at the neutral wire in
(2 marks)
this type of circuit.